Tool Primer: How to Finish your Project: Penetrating Oils

This is the second Tool Primer article on finishing your woodworking project. You can find Part One: Sanding here.

In this article I will discuss the finishes available for woodworking projects at most local big-box hardware stores. The first step is creating a clean, dust-free uniform surface by sanding all a parts to a high grit. I detailed my process in Part One. The finishing process is the difference between a good woodworking project and a heirloom piece of furniture. When I want to really knock a project out of the park, I focus much of my energy on choosing and creating a proper finish.

Keep reading for the breakdown and uses of the common penetrating oils found in your local big box home improvement and hardware stores.

Have you ever walked into the hardware store and wandered down the finishes aisle? It’s a plethora of choices and brands, all claiming to produce great looking results. Which one is right for your project? Well, it depends on how you will use your project, what you want your project to look like and how much time you have to finish your project.

Penetrating Oils vs Surface or Film Finishes

Woodworking finishes can first be classified by how they protect the wood. Penetrating finishes, such as linseed oil and mineral oil, soak into the wood and produce low luster (meaning not very shiny) sheens. Surface or film finishes, on the other hand, lay on top of the wood and seal it from outside moisture and contaminants. They form more protective finishes and higher sheens (high gloss)

Penetrating oils have many advantages. They are easy to apply, repair easily, usually less toxic than other finishes and very, very cheap. They have disadvantages also. Penetrating oils, despite the connotations of the word penetrating, provide minimal protection from moisture, dings and usage. They also, in my experience, tend to fade over time.

While their are many bottles on the shelves which claim penetrating powers, there is only two real types of penetrating oil on the shelf of your local hardware store: boiled linseed oil and mineral oil.

Taking Care Of Business with BLO

In the olden days of yore, linseed oil was the only true finish around. Pressed or extracted from the flax plant, the oil dries slowly over time on the wood, giving your project a very distinct yellow hue. Nowadays, linseed oil is heated with petroleum solvents and metallic dryers and sold as boiled linseed oil, or BLO. Application is dead simple: soak a surface, wipe off the excess with a cloth and let it sit. It takes about a day to dry to the touch and sometime longer, depending on conditions, to cure completely. Once cured, linseed oil is food-safe.

BLO is a great undercoat in a three-part finish (undercoat, mid-coat, top-coat – more on these later). Just remember it will continue to age your wood throughout the piece’s lifetime.

Mineral Oil: Your Baby Uses It Too

Mineral oils are clear and food-safe. Most often, they will be labeled as “butcher block oil” or “salad bowl finishes”. Mineral oil deepens a wood’s natural hue, giving it an “always wet” look. It achieves this by, well, not really drying. This makes it great for things like kitchenware, bowls, spoons & cutting boards, but not suitable to projects which need a film finish applied over it. Mineral spirits, while similarly named, do dry and don’t do a thing towards finishing your work. Don’t confuse the two.

Penetrating oils make great finishes for objects which will come into heavy food use, get banged up, or which will be handled by small beings who put things in their mouths a lot. I’ve used these finishes on toys, dinnerware, bowls, cutting boards, hand tools, etc. They are quick, easy to apply and look great on their own.

What if you have a project, such as a table, chair or other doodad that will require a stronger finish? Why, start with a coat or two of BLO, then let it cure for a few days. This will give your work piece a great glow, reminiscent of old, antique furniture. Then you can apply a film finish over it!

Make it safe & keep the rubber side down this week. Thank you for visiting my practice zone and project showcase. If you wish to lend your support for this site, please like WoodshopCowboy on Facebook or follow me on Twitter. If you are interested in making and education, why not check out Work Notes, a curated set of articles from the web, published every week?